Hot Tub Temperature Sensor Troubleshooting

If you have a faulty hot tub thermostat and can’t get your hot tub to heat up as expected, then this detailed guide on hot tub temperature sensor troubleshooting is exactly what you need!

The process for increasing or decreasing the temperature on your spa has evolved dramatically over time. In the past, you had to do the whole thing manually.

However, with advanced hot tubs, there are sensitive thermostats installed that improve their performance dramatically.

Advanced hot tubs are now equipped with a LCD display that has a range of buttons that connect directly with the controller.  These can be used to increase or decrease the temperature according to your preferences.

The temperatures shown are within defined limits that are deemed safe. A temperature probe is fitted on the controller that constantly takes readings of the temperature of the water.

In the older models, there was a dial thermostat that had a variance of up to five degrees, so the water was likely to get hotter or colder depending on other factors.

But, there are a whole lot of other things that come into play, especially when you have to troubleshoot your hot tub.

Hot Tub Temperature Sensor Troubleshooting

If the water is slightly warm in your tub and yet it is not reaching the original temperature that you set, it could be due to a number of reasons.

This may be caused due to clogged pipes, dirty filters, a damaged pump, or a faulty temperature sensor. In case the water doesn’t get hot at all, there is a pretty strong chance that something is wrong with the heater.

Your hot tub is designed to get warm enough so that the moment you get in, you are able to feel relaxed. But, what happens when your hot tub doesn’t get hot enough?

There are a plethora of elements that are responsible for making sure that the temperature in your hot tub rises to an appropriate extent.

If the temperature doesn’t get hot enough, it could be due to a damaged thermostat or a faulty high-limit sensor, in addition to the reasons given above.

While there are a few fixes that you can implement by yourself, most of them will require you to hire a professional to do the job.

Hot tubs are expensive, and most people don’t really feel comfortable working with electrical components and wiring and water in such close proximity.

How Do You Calibrate a Hot Tub Thermostat?

If you are having problems with the water not reaching the desired temperature properly, you may want to start off by adjusting the thermostat.

Again, this is only possible if you have an older hot tub that comes with a dial thermostat. The newer variants generally come with a temperature sensor that must be inserted into the thermal well.

This ensures that the hot tub comes into immediate contact with water. The sensor works in tandem with the display panel, thus showing you the appropriate temperature, and both of these are connected to the control box.

You also have to take a look at the high-limit sensor. This sensor is automatically triggered when the temperature reaches higher levels, and is usually not connected to the panel at the top.

In case the high-limit sensor is malfunctioning, it could prevent the hot tub from heating up properly. For older hot tubs that have a knob thermostat, you can easily calibrate it.

To do so, the first step is to check the water and the filter in the hot tub. You need to ensure that the filter is clean and not clogged, and then ensure that there’s adequate amounts of water in the hot tub.

You also need to ensure that there is no clogging in the jets. Then, you need to start by checking the temperature probe. This is usually found on the bottom of the hot tub (you need to look at it from below), and connects directly to the metal tip and the controller.

This is the component that is pushed into the thermal well. You will want to ensure that the component is firmly inserted within the thermal well. If it isn’t, it’s not going to give accurate readings.

The next step is to check the temperature of the water. You should dial up the temperature to the maximum of 104 and see if it rises. If it was previously primed at 98 degrees, it should take around an hour or so to reach 104 degrees.

Then, use a thermometer to check the temperature of the water, and then compare it with the temperature that is shown on the display. If the two are not matched, you need to calibrate them again.

If the thermostat has a flat screw or an Allen screw, you can easily calibrate it with ease. If it doesn’t have a screw altogether, it might be a wise idea to call a heating engineer or a hot tub expert to your place to fix the problem.

If you have a newer model, you may want to check whether the temperature probe has been thrust deep in the back.

It should be snugly fitted in the thermal well, and if it isn’t going in, you may want to consider replacing it altogether. If that doesn’t resolve the problem, you will have to replace the topside panel altogether.

The good thing about this is that temperature probes are generally quite inexpensive, and you can easily replace them without much of a hassle.

How Do You Change a Thermostat on a Hot Tub?

If you have tried calibrating the hot tub and it doesn’t work, your only option will be to change the thermostat altogether. A bad thermostat could prove to be the root of the problem, and you need to follow a series of steps to change it.

The first step is to deactivate the power to your hot tub. Go to the power panel close to the top of the hot tub and then remove the power connection.

Then, unscrew the main covering from your hot tub, and find the thermostat. You need to disconnect the wiring from the main control unit as well as the temperature probes.

Take out the tiny thermostat (you might have to unscrew a few screws to remove it in some cases). Then, put in the new replacement and reconnect the wiring.

You will have to screw the panels back in, and then tighten the main panel. Once you are done, just turn on the hot tub and see if it starts working again. That’s it, you have changed the thermostat!

If the hot tub starts warming up normally and the temperature reading indicates the right temperature, you may have resolved the problem.

But, if the temperature doesn’t show and the hot tub is still not heating up, it’s probably because of the temperature sensor in the hot tub.

You can actually use your hot tub if the water isn’t hot; you can heat up the water gently by harnessing the heat from the sun.

Just put the cover on and let the water heat up for a while before you get in. Obviously, the water will never be as hot as you might like, but it’s still better than sitting in a tub of cold water!

How Do You Test a Hot Tub Temperature Sensor?

Here are just a few tips to help you test the temperature of your hot tub. The first step is to turn off the main power supply directly from the main power panel.

Then, you should set the resistance meter to show 20,000 Ohms. Look for the sensor wire, and then unplug it straight from the control box.

The next step is to place all the main connectors of the ohm meter on to the green and the red wires, and then check the readings with the temperature chart.

If the water in the tub does not heat up in the right fashion, or if it’s not showing the right temperature, you should probably consider testing the temperature sensor and identify the cause of the problem.

A majority of the sensors available nowadays usually have a maximum resistance of 10,000 at a normal 77 degrees F.

As the water starts getting colder, the readings can rise to 50,000, but if placed in the hotter water, the readings are going to be much lower.

The first thing you need to do is check the instruction manual that was sent by the hot tub manufacturer. You can check if the readings are appropriate or not.

The Bottom Line

If you have gone through all the details specified in this article, finding the thermostat on your hot tub is going to be quite easy for you.

However, it’s not as easy to figure out what’s wrong with the hot tub and then fix the problem. It’s important for you to understand your limitations.

Do not mess with the hot tub if you don’t know what you are doing, as you could end up causing damage to the whole thing as well.

It’s recommended that you avoid tinkering with the hot tub all on your own as that could lead to a myriad of problems.

You may end up causing more damage to the hot tub in your desire to fix it, so it’s best to avoid doing this if you are inexperienced in it.

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